Environment maps are used to create perspective views of a curved panoramic scene. An environment map is an image depicting the appearance of a scene, as it is perceived when viewed from a specific location. Perspective views are obtained by mapping the environment map onto appropriate view planes.
Cylindrical environment maps are used in the Apple QUICKTIME.RTM. software system. A camera is positioned in a fixed location, and multiple photographs are taken as the camera swivels in azimuth. The photographs are digitized and processed by a "stitcher" to produce a warped panorama. The QUICKTIME.RTM. player employs projective geometry to project the panorama onto a view plane which changes in response to interactive panning and zooming, controlled by a user.
In U.S. Pat. No. 5,396,583 entitled CYLINDRICAL TO PLANAR IMAGE MAPPING USING SCANLINE COHERENCE, the disclosure of which is hereby incorporated by reference, there is described a method and system for optimizing the speed of the projective warping calculation for cylindrical environment maps by decomposing the warping calculations into horizontal scanline scaling followed by vertical scanline scaling. The horizontal and vertical scalings are one-dimensional, and as such can be carried out rapidly.
In U.S. Pat. Nos. 5,446,833 and 5,561,756 relating respectively to a TEXTURE SPHERE ENVIRONMENT MAP RENDERING METHOD AND SYSTEM the disclosure of which is hereby incorporated by reference, there is described a method and system for optimizing the speed of the projective warping calculation for spherical environment maps.